Pretreatment apparatus for removing pith from cornstalk, pulp manufacturing method using cornstalk, and paper manufacturing method using cornstalk pulp

ABSTRACT

A pretreatment apparatus for removing pith from cornstalks and separating husks therefrom includes a casing that receives cornstalks in a free-fall manner through an upper side thereof and allows the corn stalks to be discharged through a lower side thereof, and a rotor inserted into the casing and rotating inside the casing to hit cornstalk chips. The rotor includes a shaft inserted into the casing to be rotated by external force, a cover member holding the shaft so as to allow rotation of the shaft therein and connected to the entirety or part of an open upper side of the casing, and a hitting unit formed on a circumference of the shaft and hitting the corn stalks input into the casing.

BACKGROUND

1. Technical Field

The present invention relates to a pretreatment apparatus for cornstalk chips, and more particularly, to a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom, a pulp manufacturing method using cornstalks, and a paper manufacturing method using cornstalk pulp.

2. Description of the Related Art

Generally, paper is made from wood pulp as a main raw material. For countries suffering from lack of wood resources, pulp has been produced using herbaceous plants, such as straw, bagasse, reeds, and the like. Further, pulp production is carried out in small scale in home industries, thereby providing very low grade paper and many difficulties including insufficient dewatering in a paper manufacturing process. Such circumstances lead to prejudice in favor of wood pulp as raw materials for high grade paper. However, rapid industrial development and urbanization have occurred together with severe environmental problems such as destruction of the ozone layer, global warming, and the like, thereby causing severe problems threatening human existence, such as variation of the ecological system, rapid climate change, and the like.

Such an environmental change leads to participation of many developed countries having high carbon emission into the Climate Change Convention, and to creation of emission trading markets, thereby promoting various endeavors of industrial circles to secure certified emission reduction and bio-energy.

Indonesia has been known as a major timber producing country, but suffers from severe depletion of wood resources leading to dramatic reduction in wood pulp production. Brazil, called the lung of the earth, also suppresses harvesting. Such change has caused not only an increase in the price of wood pulp, but also severe competition for securing pulp for paper manufacture. Such a global trend promotes an interest in renewable fiber resources having a relatively short period of growth.

For example, attempts have been made to provide pulp resources through cultivation of kenaf having a relatively short period of growth, and to use fast growing tropical hardwoods as pulp materials through reforestation. However, fundamental solutions have yet to be found in the art in spite of such endeavors. Accordingly, development of pulp resources based on annually renewable herbaceous plants and to agricultural waste has attracted interest.

In particular, herbaceous plants have very different characteristics from wood in terms of morphological and chemical features. Although bast fibers and some herbaceous plants are longer than wood pulp fibers, most herbaceous plants contain a large amount of slenderer or shorter parenchyma than wood pulp. As a result, herbaceous plants suffer from dewatering problem and low strength when used as a raw material for paper, making it difficult to achieve commercialization thereof, and have been used as a raw material for low grade paper in underdeveloped countries or other countries suffering from lack of wood resources. Although there are some herbaceous plants having chemical properties similar to softwood, general herbaceous plants tend to have a low amount of lignin and a high amount of hemicellulose.

Cornstalks constitute agricultural waste and the amount of cornstalks produced is second only to straw. Most cornstalks have specific applications and thus are discarded except for some cornstalks used as feed for animals. Thus, development of cornstalk pulp will lead not only to environmental protection through conversion of waste into fiber resources but also to significant improvement in rural household incomes.

In particular, since cornstalks have a longer fiber length and a slenderer than hardwoods, it is anticipated that there will be difficulty securing bulkiness of paper. However, since the cornstalks have a much lower amount of lignin and a higher amount of hemicellulose than wood, the cornstalks exhibit chemical characteristics suited to paper manufacture.

Since cornstalk pith is composed of very fine parenchyma cells and contains large amounts of silica, the pith can cause many problems in application of cornstalks to pulp for paper. A technique for separating pith from cornstalks is not developed in the art, and thus cornstalks are not widely used as raw materials for high grade paper. In particular, when there are large amounts of parenchyma having a very small cell size, it is difficult to improve the production speed due to inferior dewatering during papermaking, and web breakage frequently occurs. As a result, use of cornstalks is restricted to production of low grade packaging paper even in China, which is one major cornstalk producing country.

A conventional apparatus for removing pith from cornstalks requires a very complicated process, which includes splitting the cornstalks in a longitudinal direction, arranging the split cornstalk pieces in a predetermined direction, compressing the arranged pieces to flatten and widen the cornstalk pieces, and scraping out pith therefrom. Thus, such a conventional pith removal apparatus has too low yield to be used for a pulp plant, which must treat tens to hundreds of thousands of tons of cornstalk chips. Therefore, there is a need for an improved pretreatment apparatus which can overcome such problems of the related art.

BRIEF SUMMARY

The present invention is directed to solving such problems of the related art, and provides a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom, which enables mass production of high grade pulp using cornstalks, and a paper manufacturing using cornstalk pulp. The cornstalk pith deteriorates yield and quality of pulp, increases consumption of treatment chemicals, and causes difficulty in recovery of the chemicals used for pulping due to large amounts of silica contained therein. Thus, the provision of a technology capable of removing pith from cornstalks is the most important issue in achieving mass production of high grade pulp using cornstalks.

Further, the present invention is directed to providing a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom, a pulp manufacturing method using cornstalks, and a paper manufacturing method using cornstalk pulp, which can produce paper having various characteristics applicable to wrapping paper for industries, toilet paper and tissue paper, printing paper, and the like through improvement of merits of cornstalk pulp while preventing disadvantages in terms of bulkiness.

In accordance with an aspect of the present invention, a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom includes: a casing which receives cornstalks in a free-fall manner through an upper side thereof and allows the corn stalks to be discharged through a lower side thereof; and a rotor inserted into the casing and rotating inside the casing to hit cornstalk chips, the rotor including a shaft inserted into the casing to be rotated by external force, a cover member holding the shaft so as to allow rotation of the shaft therein and connected to the entirety or part of an open upper side of the casing, and a hitting unit formed on a circumference of the shaft and hitting the corn stalks input into the casing.

The hitting unit may include a plurality of plates disposed in an axial direction of the shaft and a plurality of bars disposed along an edge of each plate.

The hitting unit may include a hitting rib detachably attached to the bar and hitting the cornstalks falling through the lower side of the casing.

The bar or the hitting rib may have a curved section.

The shaft may be connected to a gear box to allow adjustment of rotational speed thereof.

The casing may include a baffle formed on an inner surface thereof to enhance hitting force with respect to the cornstalks.

The casing may be formed at an upper side or circumference thereof with an input gate through which the cornstalks are supplied into the casing, and the cornstalks may be continuously supplied by a caterpillar feeder or conveyer belt when poured into the input gate of the casing.

The casing may include a vibrating screen unit which divides the cornstalks according to the size of the corn stalks while the cornstalks are hit and falling down.

The vibrating screen unit may include a frame placed below the casing to discharge the cornstalks hit and falling down, a group of mesh screens slantly stacked inside the frame and disposed to have mesh sizes gradually increasing from a lower side to an upper side to sieve cornstalks corresponding to the respective mesh screens, a discharge hole formed on a circumference of the frame to discharge the cornstalks sieved by the respective mesh screens, and a vibrator vibrating the frame.

The cornstalks divided and sieved according to size of the cornstalks may be returned to the casing by a feedback feeder.

In accordance with another aspect of the present invention, a pulp manufacturing method using a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom includes: cutting cornstalks to a length of 10 to 60 mm, hitting the cornstalk chip using a rotating hitting device, and performing cornstalk pretreatment to sieve husk and pith of the cornstalks, and fragments of the husk.

The method may further include cooking cornstalk chips obtained by the cornstalk pretreatment using sodium hydroxide and/or the mixture of sodium hydroxide and sodium carbonate.

The cooking may be performed in a 12 to 16% active alkali at a liquor ratio of 3:1 to 6:1 and a temperature of 120 to 150° C. for 60 to 150 minutes.

The cooking may include adding 0.05 to 0.2% anthraquinone to increase pulp yield and to minimize dissolution of hemicellulose.

A further aspect of the invention provides a method of manufacturing industrial paper from 100% unbleached cornstalk pulp, or from the mixture of cornstalk pulp and unbleached softwood bleached kraft pulp or unbleached hardwood kraft pulp manufactured by the method.

Still another aspect of the invention provides a method of manufacturing toilet paper and tissue paper using the bleached cornstalk pulp manufactured by the method.

Yet another aspect of the present invention provides a method of manufacturing printing paper by performing mechanical treatment to bleached cornstalk pulp, and mixing the bleached cornstalk pulp with at least one of softwood bleached chemical pulp, hardwood bleached chemical pulp, and bleached chemi-thermo-mechanical pulp.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the present invention will become apparent from the following description of exemplary embodiments given in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram of a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom according to one exemplary embodiment of the present invention;

FIG. 2 is a side view of a rotor of the pretreatment apparatus according to the exemplary embodiment of the present invention;

FIG. 3 is an exploded view of the pretreatment apparatus according to the exemplary embodiment of the present invention, showing the rotor separated from a casing of the pretreatment apparatus;

FIG. 4 is a perspective view of the rotor of the pretreatment apparatus according to the exemplary embodiment of the present invention;

FIG. 5 is an exploded perspective view of a hitting unit of a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom according to another exemplary embodiment of the present invention;

FIG. 6 is a plan view of mesh screens provided to the pretreatment apparatus for removing pith from cornstalks and separating husks therefrom according to the exemplary embodiment of the present invention;

FIG. 7 is a flowchart of a pulp manufacturing method using a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom according to one exemplary embodiment of the present invention;

FIG. 8 is pictures of cornstalks cut to 1.5 cm, 3 cm, 6 cm and 10 cm by a cornstalk chip pretreatment apparatus according to one exemplary embodiment of the present invention;

FIG. 9 is pictures of wet cornstalks and dried cornstalk chip treated by a hitting device used for a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom according to one exemplary embodiment of the present invention; and

FIG. 10 is a flowchart of a process of preparing cornstalk chips and separating husks from cornstalk using the pretreatment apparatus according to the exemplary embodiment of the present invention.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the drawings are not to precise scale and may be exaggerated in thickness of lines or size of components for descriptive convenience and clarity only. Furthermore, the terms used herein are defined by taking functions of the present disclosure into account and can be changed according to user or operator's custom or intention. Therefore, definition of the terms should be made according to the overall disclosure set forth herein.

FIG. 1 is a diagram of a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom according to one exemplary embodiment, FIG. 2 is a side view of a rotor of the pretreatment apparatus according to the exemplary embodiment, FIG. 3 is an exploded view of the pretreatment apparatus according to the exemplary embodiment, showing the rotor separated from a casing of the pretreatment apparatus, and

FIG. 4 is a perspective view of the rotor of the pretreatment apparatus according to the exemplary embodiment.

FIG. 5 is an exploded perspective view of a hitting unit of a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom according to another exemplary embodiment of the present invention.

FIG. 6 is a plan view of mesh screens provided to the pretreatment apparatus for removing pith from cornstalks and separating husks therefrom according to the exemplary embodiment of the present invention.

FIG. 7 is a flowchart of a pulp manufacturing method using a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom according to one exemplary embodiment, FIG. 8 is pictures of cornstalks cut to 1.5 cm, 3 cm, 6 cm and 10 cm by a cornstalk chip pretreatment apparatus according to one exemplary embodiment, and FIG. 9 is pictures of wet cornstalks and dried cornstalk chip treated by a hitting device used for a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom according to one exemplary embodiment.

FIG. 10 is a flowchart of a process of preparing cornstalk chips and separating husks from cornstalk using the pretreatment apparatus according to the exemplary embodiment.

Referring to FIGS. 1 to 4, the apparatus for removing pith from cornstalks and separating husks therefrom according to the exemplary embodiment includes a casing 100 and a rotor 200.

The casing 100 receives cornstalks in a free-fall manner through an upper side thereof and guides the cornstalks to be discharged through a lower side thereof. Although the casing 100 is illustrated as having a cylindrical shape in this embodiment, it should be understood that the casing 100 may be modified in various ways. The casing 100 may be made of various materials.

Specifically, the casing 100 is configured to allow cornstalks to fall free therein. This structure of the casing 100 allows continuous supply of cornstalks and immediate discharge of cornstalk chips obtained by hitting the cornstalks, thereby preventing the chips from being accumulated within the casing 100.

The rotor 200 is axially inserted into casing 100. The rotor 200 is rotatably received within the casing 100. Thus, cornstalks are supplied into the casing 100 through the upper side thereof, hit inside the casing 100, and discharged as chips through the lower side thereof.

Specifically, the rotor 200 includes a shaft 210, a cover member 220, and a hitting unit 230.

The shaft 210 is axially inserted into the casing 100. That is, the shaft 210 is received inside the casing 100 to stand vertically therein. Further, the shaft 210 is rotated in one direction by a drive motor 212. Drive force of the drive motor 212 may be converted into rotational force in various ways when transferred to the shaft 210.

The cover member 220 holds the shaft 210 at a fixed place and prevents cornstalks from colliding against the rotor 200 and scattering upwards in the casing 100.

Specifically, the cover member 220 is detachably coupled to the upper side of the casing 100 and holds the shaft 210 to be rotated at the center thereof. Although not shown in the drawings, the shaft 210 is provided with a ball bearing to prevent friction with the cover member 220 during rotation of the shaft 210.

Particularly, the cover member 220 is formed to cover the entirety or part of the open upper side of the casing 100.

When the cover member 220 is configured to cover the entirety of the open upper side of the casing 100, the casing 100 is formed at an upper portion of the circumference thereof with an input gate 110 through which cornstalks are supplied to the casing 100. Here, the input gate 110 is formed at the upper portion of the circumference of the casing 100 in order to allow cornstalks to be hit as much as possible within the casing 100 by increasing hitting time of the cornstalks within the casing 100.

Further, when the cover member 220 is configured to cover part of the open upper side of the casing 100, the open upper part of the casing 100 serves as the input gate 110. Obviously, the cover member 220 may be modified to have various shapes and may be detachably coupled to the upper side of the casing 100 in various ways such as bolting or the like. In addition, although the cover member 220 can be detachably coupled to the lower side of the casing 100, it is advantageous that the cover member 220 is provided to the upper side of the casing 100 for ensuring smooth discharge of cornstalk chips.

Further, the hitting unit 230 is provided to the circumference of the shaft 210 and directly hit cornstalks input through the input gate 110 of the casing 100. The hitting unit 230 may be secured to the shaft 210 to apply as high hitting force as possible to cornstalks via rotating force of the shaft 210.

Specifically, the hitting unit 230 includes plates 232 and bars 234. A plurality of plates 232 is provided to the circumference of the shaft 210. Here, the plates 232 are arranged in an axial direction of the shaft 210, and may have various shapes and may be formed of various materials.

Further, the plates 232 are securely coupled to the shaft 210 in various ways such as clamping and the like. Of course, the plates 232 may be integrally formed with the shaft 210. The number of plates 232 is not particularly limited.

A plurality of bars 234 is arranged along an edge of each of the plates 232. Here, the bars 234 are paired and serve to hit cornstalks. Specifically, each pair of bars 234 is comprised of bars which have different lengths and are alternately arranged with other bars. This arrangement increases hitting force with respect to cornstalks. The bars 234 may be detachably attached to the plates 232.

Here, each of the bars 234 has a rounded section 238. The rounded section 238 is formed at a peripheral surface of the bar 234, which will be brought into direct contact with cornstalks, and serves to separate the cornstalks into husks and pith by hitting the cornstalks. The rounded sections 238 of the bars 234 make it possible to separate the cornstalks into husks and pith without pulverizing the cornstalks.

In addition, the shaft 210 is connected to a gear box 214 to allow adjustment of rotating speed thereof. That is, in order to prevent cornstalks from being pulverized due to excessively strong hitting of the bars 234 against the cornstalks, the rotating sped of the shaft 210 is adjusted. The gear box 214 connects the drive motor 212 to the shaft 210.

Alternatively, as shown in FIG. 5, the hitting unit 230 may include plates 232, bars 234, and hitting ribs 236.

A plurality of bars 234 is disposed along an edge of each of the plates 232. Each of the bars 234 supports the hitting rib 236. Here, the bars 234 may be integrally formed with each of the plates 232 or may be detachably coupled thereto. For convenience of description, the bars 234 are illustrated as being detachably coupled to each of the plates 232 by bolting. Obviously, the number and shape of bars 234 are not particularly limited.

In addition, each of the hitting ribs 236 is detachably coupled to the corresponding bar 234 and serves to hit cornstalks falling down within the casing. In other words, cornstalks are directly hit to become chips by the hitting ribs 236. The hitting rib 236 may be detachably coupled to the bar 234 or may be integrally formed therewith. For convenience of description, the hitting ribs 236 are illustrated as being detachably coupled to the bars 234 by bolting.

In particular, each of the hitting ribs 236 may be formed on a side surface of the bar 234 facing a rotational direction of the bar 234 to hit cornstalks as strong as possible. Of course, the hitting ribs 236 may have various shapes.

Here, separation of the hitting ribs 236 from the bars 234 is performed for replacement or reparation of the hitting ribs 236 worn out due to use for long duration. Of course, the bars 234 may be replaced when the hitting ribs 236 are integrally formed with the bars 234.

Each of the hitting rib 236 has a rounded section 238. The rounded section 238 is formed at a peripheral surface of the hitting rib 236, which is brought into direct contact with cornstalks, and serves to separate cornstalks into husks and pith by hitting the cornstalks. The rounded sections 238 of the hitting ribs 236 make it possible to separate the cornstalks into husks and pith without pulverizing the cornstalks.

In addition, the shaft 210 is connected to the gear box 214 to allow adjustment of rotating speed thereof. That is, in order to prevent cornstalks from being pulverized due to excessively strong hitting of the hitting ribs 236 against the cornstalks, the rotating sped of the shaft 210 is adjusted. The gear box 214 connects the drive motor 212 to the shaft 210.

On the other hand, since the shaft 210 and the hitting unit 230 are rotated within the casing 100, a whirling motion is generated within the casing 100, causing the cornstalks supplied into the casing 100 to rotate along an inner wall of the casing 100. As a result, the cornstalks are not brought into direct contact with the hitting ribs 236, so that the degree of hitting by the hitting ribs 336 is reduced.

Thus, the casing 100 is formed on an inner surface thereof with a baffle 300 to increase hitting force with respect to cornstalks. The baffle 300 is formed vertically on the inner surface of the casing 100 and hits cornstalk chips moved along the inner wall of the casing 100 due to the whirling motion within the casing.

The baffle 300 may be integrally formed with the casing 100 or may be detachably coupled thereto. The baffle 300 may be modified in various ways, and the number of baffles is not particularly limited.

Cornstalks may be automatically continuously supplied to the input gate 110. Such automatic continuous supply of cornstalks is performed to increase the hitting amounts of corns-stalks as much as possible within a preset operation time.

Thus, cornstalks are continuously supplied to the input gate 110 by a caterpillar feeder 400. Here, the caterpillar feeder 400 is configured to continue to rotate so as to allow the cornstalks to be continuously supplied to the input gate 110. For example, the caterpillar feeder 400 may be a conveyor belt wound around a pair of rollers, which is forcibly rotated.

Further, cornstalks hit by the hitting ribs 235 while falling free within the casing 100 may have various sizes in a chip state. Thus, the hit cornstalks may be divided according to size thereof in a chip state.

Accordingly, the casing 100 may be provided with a vibrating screen unit 500 which separates cornstalks according to size when the cornstalks are hit and fall down.

Here, the vibrating screen unit 500 includes a frame 510, a group of mesh screens 520, discharge holes 530, and a vibrator 540.

The frame 510 is placed below the casing 100 and configured to discharge the cornstalks hit and falling down from the casing 100. For convenience of description, the frame 510 has a barrel shape open at upper and lower sides thereof.

The group of mesh screens 520 includes a plurality of mesh screens 522,524 stacked inside the frame 510. Here, although each of the mesh screens 522,524 may be integrally formed with the frame 510, it is advantageous that the plural mesh screens 522, 524 be detachably mounted therein.

As shown in FIG. 6, although the mesh screens 522, 524 may have an identical mesh size, it is advantageous that the mesh screens 522,524 have different mesh sizes in order to sequentially separate the cornstalks according to size. For convenience of description, two mesh screens 522,524 are provided in this embodiment.

More specifically, the mesh screens 522,524 are disposed to have mesh sizes gradually increasing from a lower side to an upper side to sieve cornstalks corresponding to the respective mesh screens. That is, a first mesh screen 522 disposed at the upper side has a greater mesh size than a second mesh screen 524 disposed at the lower side.

In addition, cornstalk chips sieved by the first mesh screen 522 and cornstalk chips sieved by the second mesh screen 524 may be discharged to preset places.

Thus, the first mesh screen 522 and the second mesh screen 524 are slanted with respect to the bottom of the frame 510. Further, the first mesh screen 522 may be disposed parallel to the second mesh screen 524.

The discharge holes 530 are formed on a circumferential surface of the frame 510 to discharge the cornstalks sieved by the first and second mesh screens 522, 524. Here, the discharge holes 530 may be formed on the circumferential surface of the frame 510 corresponding to the first and second mesh screens 522, 524, respectively.

Accordingly, the cornstalks sieved by the first and second mesh screens 522, 524 are discharged in a chip state from the frame 510.

Further, when the first and second mesh screens 522, 524 are vibrated, the sieved cornstalk chips are efficiently discharged through the discharge holes 530, so that the first and second mesh screens 522, 524 are not blocked by the cornstalk chips.

Thus, the frame 510 is provided with the vibrator 540 to shake the frame 510 or to vibrate the first and second mesh screens 522, 524.

Here, the vibrator 540 includes a motor 542, an eccentric shaft 544, and a power transmission member 546 connecting the motor 542 to the eccentric shaft 544 such that the frame 510 can be vibrated by eccentric force when the eccentric shaft 544 is rotated by the motor 542. The power transmission member 546 may be realized in various ways, such as a combination of a belt and a pulley, a combination of a chain and a sprocket, and the like.

Particularly, cornstalk chips having a size of a preset value or less passing through the second mesh screen 524 may be received in a storage barrel 548. The storage barrel 548 may be detachably attached to a lower side of the frame 510.

Further, the cornstalks separated according to size and discharged through the discharge holes 530 may be supplied again into the casing 100 and subjected to repeated hitting.

Thus, the cornstalks separated according to size and discharged through the discharge holes 530 may be supplied again into the casing 100 by a feedback feeder 600.

The feedback feeder 600 is connected to the caterpillar feeder 400 and may continuously rotate to allow the cornstalks to be continuously supplied to the caterpillar feeder 400. For example, the feedback feeder 600 may be a conveyor belt wound around a pair of rollers, which is forcibly rotated.

Referring to FIG. 7, a pulp manufacturing method using a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom according to one exemplary embodiment includes a cutting operation S10, a hitting operation S20, a cornstalk pre-treatment operation S30, and a cooking operation S40.

The cutting operation S10 is a process of cutting cornstalks to a length of 10 to 60 mm.

If the cornstalks are cut to a length less than 10 mm, the cornstalks suffers from severe cutting of fibers, and if the cornstalks are cut to a length exceeding 60 mm, the cornstalks suffers from insufficient separation of the pith and the outer cover.

The cutting operation S20 is a process of hitting the cut cornstalks using a rotating hitting device. Here, the rotating hitting device refers to the hitting unit described above.

The cornstalk pretreatment operation S30 is a process of sieving husks and pith of the cornstalks, and fragments of the husk. The cooking operation S40 is a process of cooking the cornstalk chips obtained by the cornstalk pretreatment using sodium hydroxide and/or mixture of sodium hydroxide and sodium carbonate.

Here, the cooking operation S40 may be performed in a 12 to 16% active alkali at a liquor ratio of 3:1 to 6:1 and a temperature of 120 to 150° C. for 60 to 150 minutes

Further, for the cooking operation S40, anthraquinone may be added in an amount of 0.05 to 0.2% to minimize decomposition of hemicellulose while increasing pulp yield.

Particularly, a pretreatment method using cornstalks according to one exemplary embodiment of the invention provides techniques of manufacturing pulp for high grade paper using cornstalks, preparing raw materials for industrial packaging paper using cornstalks or producing toilet paper and tissue paper using cornstalks through bleaching. Further, the pretreatment process may solve quality problems of paper manufactured by cornstalk pulp and produce high grade printing paper through suitable combination of bleached cornstalk pulp with softwood bleached chemical pulp, hardwood bleached chemical pulp), bleached chemi-thermo-mechanical pulp (BCTMP), which exhibit various characteristics.

The most important issue in production of economically high grade pulp from cornstalks is to remove parenchyma having a relatively short fiber length and pith containing a large amount of silica from the cornstalks. Insufficient removal of the parenchyma and pith causes an increase in consumption of treatment chemicals and a decrease in pulp yield. Further, a large amount of parenchyma constituting fines is contained in the manufactured pulp, so that dewatering is poorly performed, thereby making it difficult to increase the paper processing speed while deteriorating paper strength. Further, chemical additives for various functions of paper can be selectively adsorbed to parenchyma, thereby deteriorating performance of the additives.

It can be seen from FIG. 8 that efficient removal of pith from cornstalk husks is significantly related to a cutting length of the cornstalks. If the length of the cut cornstalk is too long, the pith is not likely to be separated from the cornstalk when external force is applied to the cornstalk. In this study, it can be seen that pith can be easily separated from a husk of a cornstalk when the cornstalk was cut to a length of 15 to 60 mm. FIG. 9 shows results of hitting wet cornstalks and dry cornstalks using the device described above.

Based on the results of this study, a system for preparing cornstalk chips and separating husks therefrom as shown in FIG. 10 was suggested to manufacture high grade pulp.

The system for preparing cornstalk chips and separating husks therefrom is configured to perform cutting cornstalks to a length of 15 to 60 mm to prepare cornstalk chips, hitting the cornstalk chips, and classifying the cornstalk chips according to size through first and second mesh screens 522, 524.

The chips having a length of 15 to 30 mm are hit by a hitting device. Referring to FIG. 2 to FIG. 4, the hitting device includes a plurality of bars 234 having different lengths and alternately arranged to perform centrifugal hitting of the chips while being rotated at 500 to 3,000 rpm by a drive motor 212 having high horse power. Then, 2 to 4 mesh chips are sieved by the first mesh screen 522. Here, the coarse chips sieved by the first mesh screen 522 are returned to the casing 100, and chips passing through the first mesh screen 522 are sieved by the second mesh screen 524. The fines and pith passing through the second mesh screen 524 are used as fuel for boilers or fodder for stocks. The chips sieved by the second mesh screen 524 are stored in silo or sent to a digester to be used for pulp manufacture.

As shown in Table 1, since cornstalks has a low content of lignin and a high content of hemicellulose unlike wood, the cornstalks can be readily manufactured into pulp. Although various pulping processes applicable to manufacture of wood pulp, such as a kraft process, a sulfite process, soda-AQ process, and the like, may also be applied to cornstalk pulp manufacture, delignification of cornstalk can be sufficiently achieved only through the soda process. Thus, as cooking chemicals, NaOH is used, and Na₂CO₃ may be mixed therewith, as needed. The amount of cooking chemicals is set to have 12 to 16% of an active alkali based on the concentration of Na₂O, thereby enabling manufacture of higher degree of pulp through a cooking process under mild conditions. As such, the cooking operation is performed under such mild conditions, thereby allowing elimination of pre-treatment using cellulose protection additives such as MgCl₂ or MgCO₃. It is possible to reduce cost for treatment chemicals and energy while reducing production time. Furthermore, in order to minimize decomposition of hemicellulose while increasing pulp yield, 0.05 to 0.2% of anthraquinone may be added. A liquor ratio may be within the range of 3:1 to 6:1 according to desired pulp characteristics. If the liquor ratio is too high, the concentration of chemicals for cooking is lowered, thereby significantly deteriorating chemical reaction. Cooking temperature may be adjusted in the range of 120 to 150° C. Cooking time may be adjusted within the range 60 to 150 minutes according to the amount of chemicals used for cooling, the cooking temperature, and desired pulp characteristics.

TABLE 1 Comparison of cornstalk with wood in terms of chemical composition Raw material Cellulose (%) Pentosan (%) Lignin (%) Softwood 40 to 50 10 to 14 24 to 30 Hardwood 40 to 50 16 to 24 18 to 28 Cornstalk 42 to 51 26 to 28 16 to 18

After the cooking operation, the pulp is subjected to washing to remove remaining chemicals, screening as in wood pulp manufacture to remove insufficiently cooked cornstalk chips or large contaminants, and removal of foreign matter having a high specific gravity using cleaners. The chips sieved by the screen is sieved again by a vibrating screen unit, and insufficiently cooked or dissociated fiber bundle is sent again to the digester.

Unbleached cornstalk pulp is used alone or in combination with unbleached softwood kraft pulp or unbleached hardwood kraft pulp to provide raw materials for industrial packaging paper or paper boards. Here, the cornstalk pulp is subjected to a refining process to obtain sufficient strength. Since the cornstalk pulp is much weaker than wood pulp, the refining process is performed at a low intensity of 0.2 to 1.0 Ws/m. Industrial paper of a desired basis weight is produced through the refining process by adjusting freeness of the pulp to a level of 500 to 350 ml CSF.

In order to use the cornstalk pulp as raw materials for toilet paper or fine paper, the cornstalk pulp is subjected to bleaching processes. As shown in Table 1, since a cornstalk has a low content of lignin, delignification of the cornstalk can be easily achieved. Thus, unlike wood pulp, it is possible to obtain sufficiently high brightness even when the number of bleaching sequences is limited to three stages. Further, since use of elemental chlorine as bleaching agents causes generation of dioxin, an elemental chlorine free bleaching (ECF) method or a totally chlorine free (TCF) bleaching method may be applied to the bleaching sequences. Although such bleaching methods are applied to wood pulp bleaching and are generally carried out through five stages, three-stage bleaching is applied to manufacture of cornstalk pulp having brightness of 80 to 90%, since bleaching of the cornstalk pulp is easy. If cornstalk pulp having a high brightness of 90% or more is needed, four-stage bleaching may be used. As the ECF bleaching method, various bleaching sequences such as DED, DEP, DEO, DEZ, PED, PEP, DEDP, DEOZ, DEDZ, DEOP, DEPD, and the like, may be applied. Here, D represents chlorine dioxide, E represents alkaline extraction, P represents peroxide, O represents oxygen, and Z represents ozone.

When manufacturing fine paper or base paper for coating, stock preparation processes including refining, pulp blending, sizing, filler loading, and the like are performed to provide suitable properties to paper according to purpose. These processes are also applied not only to wood pulp but also all available pulp. Here, it is a core to optimize application of wood pulp blending, fillers, sizing agents, retention aids, and the like so as to compensate for drawbacks of cornstalk pulp while satisfying desired characteristics of paper to be manufactured. Thus, different features of the stock preparation processes for cornstalk pulp from those for conventional wood pulp will be mainly described herein.

As shown in Table 2, cornstalk pulp fibers have much finer than wood pulp fibers. Further, as shown in Table 1, cornstalk pulp has a high content of hemicellulose. Thus, when paper is manufactured using only bleached cornstalk pulp, the density of paper excessively increases, thereby lowering opacity. Considering that bulk and opacity are very important for fine paper, it can be easily recognized that there is a need for compensation for bulkiness and opacity when manufacturing fine paper. Even if paper is manufactured using conventional wood pulp, a mixture of softwood pulp, hardwood pulp and a small amount of BCTMP is used to compensate for disadvantages of the respective pulps.

TABLE 2 Characteristics of wood and cornstalk fibers Average fiber Average fiber Raw material length (mm) width (μm) Softwood 2.7 to 4.6 32 to 43 Hardwood 0.7 to 1.6 20 to 40 Cornstalk 1.0 to 1.5 18 to 22

As described above, since the cornstalk pulp is comprised of fine fibers to provide good flexibility and have a high content of hemicellulose to allow better fiber bonding than other pulp fibers, the cornstalk pulp may have sufficient strength simply by passing through a deflaker without the refining process. The refining process consumes a great amount of energy second to a drying process in paper manufacture. For wood pulp, a power of about 71 kW/t (hardwood) to 84 kW/t (softwood) per ton is required to decrease the freeness of 100 ml CSF through refining. Assuming 1,000 tons of pulp a day is subjected to refining, it is possible to reduce an electric energy of 71,000 kW upon application of energy for refining hardwood pulp, and it is possible to reduce an electric energy of 21,300,000 kW when the paper manufacturing system is operated for 300 days per year. As such, according to the fact that use of cornstalk pulp as raw materials for paper may result in significant reduction of manufacturing cost through elimination of the refining process, it is expected that paper manufacture using cornstalks pulp will become a good approach to overcome crisis of paper manufacturers in current situations of strengthening regulation for reduction of greenhouse gas emission.

When producing tissue paper like toilet paper, fillers for securing strength of paper are not used due to low basis weight. Particularly, toilet paper is produced by taking absorbency, disintegration in water and softness into consideration. Since cornstalk pulp has a slightly longer fiber length than hardwood pulp and has a high content of hemicellulose, the cornstalk pulp is suited to manufacture of toilet paper, tissue paper and glassine paper. As such, since the cornstalk pulp is much weaker than wood pulp but has superior bonding characteristics thereto, it is enough to provide slight impact to the cornstalk pulp two or three times using deflaker without refining when producing toilet paper. Here, the deflaker refers to equipment for imparting only weak impact to pulp fibers. Further, refining refers to a process of applying compression, tensile and shear force to pulp fibers to cause fibrillation or fiber cutting.

As shown in Table 3, when toilet paper was produced using 100% cornstalk pulp, the toilet paper exhibited excellent properties. When producing a little bulky toilet paper having absorbency like toilet paper for bidet, the toilet paper is produced by mixing 5 to 10% of softwood bleached kraft pulp, 20 to 40% of hardwood bleached kraft pulp, and 40 to 60% of cornstalk pulp. Here, when producing such toilet paper using wood pulp, slight refining is performed to adjust freeness to a level of 400 to 550 ml CSF.

When producing printing paper, bulkiness, opacity, smoothness, and the like are considered as major factors. However, since cornstalk pulp has drawbacks such as low bulkiness and opacity due to inherent characteristics thereof, the cornstalk pulp is mixed with softwood bleached chemical pulp, hardwood bleached chemical pulp, BCTMP or the like to compensate for such drawbacks of the cornstalk pulp. According to desired properties of printing paper, the mixing ratio may be set to have 1 to 5% of softwood bleached chemical pulp, 20 to 50% of hardwood bleached chemical pulp, 20 to 50% of cornstalk pulp, and 5 to 10% of BCTMP. As in production of toilet paper, the cornstalk pulp is subjected to deflaker treatment, and the softwood and hardwood chemical pulp are subjected to refining to adjust freeness to a level of 400 to 500 ml CSF.

As the fillers, precipitated calcium carbonate (PCC), ground calcium carbonate (GCC), talc, and clay may be used. The amount of fillers may be set within the range of 5 to 25% according to a desired purpose of paper to be produced.

As the sizing agents, alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), fortified rosin emulsion, and the like may be used, and the amount of sizing agents may be set within the range of 0.05 to 6%.

Since the fillers and the sizing agents are not fixed to pulp fibers by themselves, use of retention agents is needed. Examples of the retention agents may include cationic starch, amphoteric starch, cationic and anionic polyacrylamide, polyethylene imine, colloidal silica, bentonite, organic microparticle, and the like.

As such, according to the embodiments of the invention, the pretreatment apparatus for removing pith from cornstalks and separating husks therefrom, the pulp manufacturing method using cornstalks, and the paper manufacturing method using cornstalks enable mass production of high grade pulp using cornstalks generally treated as agricultural waste under very mild conditions as compared with the related art.

In addition, the paper manufacturing technique according to the invention may allow cornstalk pulp to be used in a state of unbleached pulp as raw materials for industrial paper, or may produce high grade paper for tissue paper or printing paper through suitable combination of bleached cornstalk pulp with softwood bleached chemical pulp, hardwood bleached chemical pulp, or BCTMP, which exhibit various characteristics, thereby assisting in improvement in rural household incomes and environmental protection.

EXAMPLES

The following examples are provided to confirm superiority of the present invention relating to a pulp manufacturing method using cornstalks, quality of cornstalk pulp, and paper manufacture. Therefore, it should be understood that these examples should not be construed in any way to limiting the scope of the present invention.

Example 1

Cornstalks were cut to a length of 1.5 cm, followed by hitting the cut cornstalks for 10 minutes in a high speed rotator and separating piths from husks of the cornstalks using screens. 400 g of the separated cornstalk chip was placed in a laboratory digester (4 liter capacity), and a sodium hydroxide solution containing 13% and 15% of active alkali was input thereto. The liquor ratio was set to 5:1 and the cornstalk chips were compressed by a metal weight so as to allow the cornstalk chips to be sufficiently dipped into cooking liquor, followed by cooling at 150° C. for 70 minutes, 90 minutes, and 120 minutes. After completing the cooking process, the cornstalk chips were subjected to washing, and rejects were removed from the cornstalk chips using vibrating screens. After completing the screening process, pulp yield, kappa number, and brightness of the cornstalk pulp were measured, and mechanical impact was applied to the cornstalk pulp for 10 minutes using a laboratory refining beater without attaching a weight to the beater, followed by producing a handsheet having a basis weight of 60 g/m² using a laboratory handsheet machine. The produced handsheet was subjected to humidity control for one day in a constant temperature/humidity room, followed by measurement of apparent density, tensile index and burst index based on TAPPI Standard. Test results are summarized in Table 3, and it could be seen that the pulp could be sufficiently used as raw materials for industrial paper, considering quality of the unbleached cornstalk pulp.

TABLE 3 Pulping characteristics of cornstalks and properties of unbleached pulp Active Cooking Screening Tensile alkali time yield Kappa Brightness Density index Burst index (%) (min) (%) number (%) (g/cm³) (Nm/g) (kPam²/g) 13 70 42 14.6 31.4 0.49 85 5.87 90 46.3 13.4 33.1 0.54 105 6.98 120 47.1 11.5 35.8 0.58 114 7.67 15 70 44.5 12.2 35.4 0.53 96 6.54 90 45.8 10.7 36.2 0.62 118 7.85 120 43.2 9.6 37.1 0.56 108 7.23

Example 2

In order to evaluate characteristics of toilet paper produced from bleached cornstalk pulp, handsheets were manufactured from 100% of cornstalk bleached pulp, and the produced toilet paper was compared with Korean Industrial Standards and market products. The toilet paper using the cornstalk pulp satisfied all of burst strength, tensile strength and absorbency according to Korean Industrial Standards, and had superior burst strength to the market products.

TABLE 4 Comparison of toilet paper manufactured using cornstalk pulp KS For market selling Cornstalk pulp Roll Flat Daehan (Flat) Yuhan (Flat) Basis weight (g/m²) 18 18 or more 12.5 or more 24 or more 24 or more Burst strength (kPa) 136 78 or more — 50 or more 50 or more Tensile strength 1.2 — 0.78 or more — — (N/15 mm) Absorbency (mm) 48 20 or more — — —

Example 3

In order to prove that paper exhibiting excellent properties in terms of bulkiness and opacity can be produced through combination of bleached cornstalk pulp with softwood bleached chemical pulp, hardwood bleached chemical pulp or BCTMP, laboratory studies were carried out. Ground calcium carbonate was used as fillers, and micro particles based on bentonite and cationic and anionic polyacrylamide was used as a retention agent. From test results, it could be confirmed that it is possible to improve major disadvantages of cornstalk pulp in terms of bulkiness and opacity through combination of pulp and filler addition.

TABLE 5 Physical properties of handsheets manufactured from cornstalk pulp, and the mixture of cornstalk pulp and wood pulps 50% cornstalk pulp, 100% 5% softwood pulp, 40% cornstalk pulp, 40% cornstalk pulp, cornstalk 40% hardwood pulp, 55% hardwood pulp, 10% softwood pulp, Properties pulp 5% BCTMP 5% softwood pulp 50% hardwood pulp Basis weight 70.1 70 69.8 71.2 (g/m²) Bulk (cm³/g) 1.05 1.32 1.28 1.16 Tensile index 49.5 52.1 50.4 51.7 (Nm/g) Burst index 1.92 1.89 1.86 1.78 (kPam²/g) Opacity 81.6 92.8 89.6 91.5 Ash content (%) 15 14.9 15.1 15

Although some embodiments have been provided to illustrate the present invention, it should be understood that these embodiments are given by way of illustration only, and that various modifications, variations, and alterations can be made without departing from the spirit and scope of the present invention. The scope of the present invention should be limited only by the accompanying claims and equivalents thereof. 

1. A pretreatment apparatus for removing pith from cornstalks and separating husks therefrom, comprising: a casing which receives cornstalks in a free-fall manner through an upper side thereof and allows the corn stalks to be discharged through a lower side thereof; and a rotor inserted into the casing and rotating inside the casing to hit cornstalk chips, the rotor comprising: a shaft inserted into the casing to be rotated by external force, a cover member holding the shaft so as to allow rotation of the shaft therein and connected to the entirety or part of an open upper side of the casing, and a hitting unit formed on a circumference of the shaft and hitting the corn stalks input into the casing.
 2. The pretreatment apparatus of claim 1, wherein the hitting unit comprises a plurality of plates disposed in an axial direction of the shaft, and a plurality of bars disposed along an edge of each plate.
 3. The pretreatment apparatus of claim 2, wherein the hitting unit comprises a hitting rib detachably attached to the bar and hitting the cornstalks falling through the lower side of the casing.
 4. The pretreatment apparatus of claim 3, wherein the bar or the hitting rib has a curved section.
 5. The pretreatment apparatus of claim 2, wherein the shaft is connected to a gear box to allow adjustment of rotational speed thereof.
 6. The pretreatment apparatus of claim 1, wherein the casing comprises a baffle formed on an inner surface thereof to enhance hitting force with respect to the cornstalks.
 7. The pretreatment apparatus of claim 1, wherein the casing is formed at an upper side or circumference thereof with an input gate through which the cornstalks are supplied into the casing, and the cornstalks are continuously supplied by a caterpillar feeder when poured into the input gate of the casing.
 8. The pretreatment apparatus of claim 1, wherein the casing comprises a vibrating screen unit which divides the cornstalks according to the size of the corn stalks while the cornstalks are hit and falling down.
 9. The pretreatment apparatus of claim 8, wherein the vibrating screen unit comprises a frame placed below the casing to discharge the cornstalks hit and falling down, a group of mesh screens slantly stacked inside the frame and disposed to have mesh sizes gradually increasing from a lower side to an upper side to sieve cornstalks corresponding to the respective mesh screens, a discharge hole formed on a circumference of the frame to discharge the cornstalks sieved by the respective mesh screens, and a vibrator vibrating the frame.
 10. The pretreatment apparatus of claim 8, wherein the cornstalks divided and sieved according to size of the cornstalks is returned to the casing by a feedback feeder.
 11. A pulp manufacturing method using a pretreatment apparatus for removing pith from cornstalks and separating husks therefrom, comprising: cutting cornstalks to a length of 10 to 60 mm; hitting the cut cornstalks using a rotating hitting device; and performing cornstalk pretreatment to sieve husk and pith of the cornstalks, and fragments of the husk.
 12. The method of claim 11, further comprising: cooking cornstalk chips obtained by the cornstalk pretreatment using sodium hydroxide and/or the mixture of sodium hydroxide and sodium carbonate.
 13. The method of claim 12, wherein the cooking is performed in a 12 to 16% active alkali at a liquor ratio of 3:1 to 6:1 and a temperature of 120 to 150° C. for 60 to 150 minutes.
 14. The method of claim 12, wherein the cooking comprises adding 0.05 to 0.2% anthraquinone to increase pulp yield and to minimize dissolution of hemicellulose.
 15. A method of manufacturing industrial paper through combination of 100% unbleached cornstalk pulp, unbleached softwood bleached kraft pulp or unbleached hardwood kraft pulp manufactured by the method of claim
 11. 16. A method of manufacturing toilet paper and tissue paper using the bleached cornstalk pulp manufactured by the method of claim
 11. 17. A method of manufacturing printing paper by performing mechanical treatment to bleached cornstalk pulp, and mixing the bleached cornstalk pulp with at least one of softwood bleached chemical pulp, hardwood bleached chemical pulp, and BCTMP. 